Download or read book Deconvolving Climate and Biotic Signals from Taphonomic Overprints in Deep sea Records of the Paleocene eocene Thermal Maximum written by Brittany Nicole Hupp and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Paleocene-Eocene Thermal Maximum (PETM), an ancient global warming event that occurred ~56 Ma, was closely associated with a rapid perturbation to the global carbon cycle, making the event an exceptionally-relevant analog for evaluating the future consequences of modern climate change. Here I examine deep-sea, planktic foraminifer records of the PETM from the Weddell Sea (ODP Site 690), southern Indian Ocean (ODP Site 1135), and equatorial Pacific Ocean (ODP Site 865). This dissertation seeks to (1) better characterize geochemical and biotic changes at various latitudes in response to PETM conditions through application of novel techniques, and (2) use the stratigraphic record of the PETM to assess how taphonomic processes such as sediment mixing and diagenesis have distorted deep-sea records of abrupt climate change. In chapters 1 and 2, I use stable carbon (Îþ13C) and oxygen (Îþ18O) isotope records constructed with graduated series of size-segregated planktic foraminifer shells to show how size-dependent sediment mixing has distorted the stratigraphic structure of the Site 690 PETM reference section. Chapter 3 demonstrates how the stable isotope signatures of individual foraminifer shells can be used to deconvolve the deleterious effects of sediment mixing on microfossil assemblages associated with abrupt biogeochemical perturbations. Application of this "isotopic filtering" method on the Site 865 PETM record reveals a transient but significant decrease in the diversity of tropical planktic foraminifer communities at the onset of the event, contrary to previous interpretations. Application of the aforementioned isotopic filtering method to high-latitude planktic foraminiferal assemblages of the PETM record of Site 1135 in chapter 4 revealed a similar, short-lived decrease in diversity, previously undetectable in the unfiltered assemblages. Lastly, in chapter 5, I generate parallel Îþ13C records of the carbon isotope excursion (CIE) marking the PETM in the Site 1135 section using traditional gas source mass spectrometry (GSMS) requiring analysis of whole foraminifer shells and secondary ion mass spectrometry (SIMS) where in-situ Îþ13C measurements are made on micrometer-scale domains within individual foraminifer shells. Comparison of these parallel Îþ13C records shows how GSMS analyses fail to capture the full magnitude of the CIE due to incorporated measurement of diagenetic calcite.
Download or read book Fluvial Response to the Paleocene Eocene Thermal Maximum in Western North America written by Brady Z. Foreman and published by . This book was released on 2013 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Paleocene-Eocene boundary ca. 56 million years ago is characterized by an extreme global warming event, known as the Paleocene-Eocene Thermal Maximum (PETM). The event is linked to the massive exogenic release of isotopically-light carbon into Earth's oceans and atmosphere, and is recognizable in the geologic record by an abrupt negative carbon isotope excursion in both organic and inorganic proxy records for duration of approximately 200,000 years. Previous studies indicate the PETM instigated massive changes in ocean and atmospheric circulation, which perturbed both terrestrial and marine environmental conditions and biotic systems. This study exploits the PETM to examine the effects of abrupt climate change on fluvial stratigraphy. The negative carbon isotope excursion associated with the PETM allows the timing and duration of the climate change to be identified independent of lithostratigraphic markers. Local climate shifts are constrained using circulation models, soil geochemistry, and paleobotanical records. Two areas are studied in detail, the Piceance Creek Basin of Colorado and the northern Bighorn Basin of Wyoming. In both areas anomalously thick and laterally persistent fluvial sand-bodies correlate with the PETM interval. In the Piceance Creek Basin the shift in fluvial deposition directly correlates with the onset of the PETM and persists beyond the carbon isotope excursion, whereas in the northern Bighorn Basin the shift appears to lag the isotope excursion by 10-20 thousand years and ends prior to the return to background climatic conditions. In the Piceance Creek Basin the change in sand-body geometry is associated with a shift to deeper paleoflow depths, wider channels, greater preservation of upper flow regime structures, prevalent crevasse splay deposits, and poorer drained floodplain soils. In contrast, within the Bighorn Basin there are no such changes and, apart from greater amalgamation, fluvial deposition appears to be largely unaffected by the PETM. When combined with other PETM terrestrial localities, the records demonstrate the PETM had substantial, but spatially diverse effects on basin-scale grain-size partitioning, discharge regimes, and river-floodplain dynamics. Aspects of the responses in the various basins are reminiscent of those predicted by two-dimensional basin-fill models, however, key differences highlight the role non-linearities, feedback loops, relaxation times, basin geometry, seasonality of precipitation, and vegetation factors play in determining large-scale depositional patterns. Consequently, it is concluded that short-term climatic events such as the PETM hold the potential to strongly alter basin sedimentation patterns, but that the sedimentologic-recorded climatic signal cannot be used to directly reconstruct paleoclimatic conditions. Instead a more appropriate approach is advocated that uses fluvial stratigraphy in concert with geochemical and other proxies to iteratively produce a more robust image of paleolandscape dynamics.
Download or read book The Paleocene Eocene Thermal Maximum Marine Response written by Tina M. J. Nielsen and published by . This book was released on 2008 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Environmental Impact of the Paleocene eocene Thermal Maximum on the Coastal Ocean written by Thomas G. Quattlebaum (Jr.) and published by . This book was released on 2004 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High resolution Paleoceanography and Modeling of Abrupt Warming Events on Greenhouse Earth written by Sandra Kirtland Turner and published by . This book was released on 2012 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: I begin by investigating patterns of global overturning circulation in the warm Paleocene epoch, a time when previous studies have suggested weak deep-ocean aging gradients and sluggish circulation. Using a new benthic foraminiferal stable isotope dataset from the high-latitude South Pacific, I demonstrate that deep waters formed in the Southern Pacific (probably around the Ross Sea) at least intermittently during the Paleocene. I also suggest a number of distinct reorganizations of overturning during this epoch. I continue by assessing the potential connections between a series of postulated hyperthermal events in the early-middle Eocene with the sequence of hyperthermals in the late Paleocene to early Eocene that bracket the Paleocene-Eocene Thermal Maximum (~56 Ma). Through a detailed comparison of the structure of all the suggested events in this interval, I demonstrate the similarity of most events, with the PETM and the subsequent Elmo event ~2 Myr later appearing as outliers. I also use a new method for identifying whether events appear significantly different from background variability. Finally, I adapt a threshold model to suggest that a common mechanism is plausible for all events. I extend my analysis of the multiple hyperthermal events of the Paleocene-Eocene to synthesize records of all possible hyperthermal events from ~250 to ~40 Ma. I primarily compare records of bulk carbonate carbon isotopes, but also assess other environmental consequences of each event. This study represents the first such synthesis of postulated hyperthermals. Finally, I use the GENIE model to assess the degree to which an individual deep-sea sedimentary record records the magnitude of environmental perturbation represented by an early-middle Eocene hyperthermal. I develop a method to `back' out the true excursion size by utilizing the sedimentary model in GENIE. I use model results to compare the range of and controls on inter-site variability in the size, timing, and overall duration of the event.
Download or read book The Deep sea Climate Record of the Eocene Oligocene Transition written by Victoria Emma Taylor and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Paleocene Eocene Thermal Maximum in the Southern Indian Ocean written by Laura Jean Mitchell and published by . This book was released on 2007 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fish Production and Diversity Across the Paleocene Eocene Thermal Maximum written by Douglas William Tomczik and published by . This book was released on 2014 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: A partial analog for modern global change is the Paleocene-Eocene Thermal Maximum (PETM)--a transient episode of warming and acidification at ~55.5 Ma that triggered extinctions in deep sea biotas, extensive biogeographic shifts, and the appearance of 'excursion biotas' (common occurrences of taxa restricted to the PETM interval). We analyzed the impact of the PETM on fish production and biodiversity using three deep sea sites in the Pacific and tropical Atlantic. Fossil fish teeth (ichthyoliths) mass accumulation rates show transient increases in fish production at all sites coincident with early stages of the PETM and exhibit little variation before and after the PETM. Fish tooth morphological diversity changes little across the PETM in both the equatorial Pacific and North Pacific gyre with larger changes at the equatorial Atlantic site. There is no evidence for the appearance of distinctive "excursion taxa" during the PETM, suggesting that fish experienced fewer geographic range shifts than calcareous and organic-walled plankton. The increase in ichthyolith accumulation, interpreted as export production at the PETM broadly matches published estimates of PETM export production from biogenic barium fluxes. Our findings contrast with model predictions for the next century, which suggest that increased global temperatures will lead to reduced subtropical fish production. Disparities between future Earth models and PETM data may reflect the different timescales of observation.
Download or read book Insights Into the Pace and Paleoceanography of Early Eocene Events of Global Warming written by Brandon H. Murphy and published by . This book was released on 2011 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Middle Eocene to Early Oligocene Paleoceanography of the Southern Ocean written by Steven Michael Bohaty and published by . This book was released on 2006 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Climate Change of the South Polar Region in Response to Topographic and Cryospheric Forcings During the Paleocene Eocene Thermal Maximum written by Mikaela Brown and published by . This book was released on 2019 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Paleocene-Eocene thermal maximum (PETM) occurred approximately 56 Ma and is marked by an estimated global temperature increase of 5 °C, a large negative carbon and oxygen excursion, and deep-sea carbonate dissolution. Determining the factors that contributed to and amplified this short-term global warming episode is essential to better understand the rapid responses of the climate system to perturbations in the carbon cycle. In this study, we utilize the fully coupled Community Earth System Model version 1.2 to assess the role of global topography on the climate of the South Polar Region during the PETM. When comparing the present-day topography (including ice sheets) to the topography of the PETM, a significant increase in surface air temperature is simulated, which agrees with previous studies. An increase of PETM precipitation over the Southern Ocean relative to present is linked to this warming, due to the higher atmospheric vapor concentration. A reduced meridional temperature gradient and the absence of ocean gateways near Antarctica in the PETM causes a decrease of the oceanic barotropic stream function. Ventilation of water masses inferred from the global meridional overturning circulation and an idealized age tracer in the Pacific and Atlantic Oceans suggest an increased poleward heat transport during the PETM, which is also supported by weakening western boundary currents. In summary, Eocene to present-day topographic and cryospheric differences lead to changes in atmospheric and oceanic circulation and heat transport, and consequentially impact the climatic responses globally. The opening of Southern Ocean gateways could potentially be linked to the transition to the cooler climate of the Eocene/Oligocene boundary.
Download or read book Response of Deep ocean Ostracodes to Climate Extrema of the Paleogene written by Stephen Allen Schellenberg and published by . This book was released on 2000 with total page 890 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Paleocene and Eocene Deep water Circulation Climate and Sea Level written by Dorothy Kim Pak and published by . This book was released on 1996 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book CO2 driven ocean circulation changes as an amplifier of Paleocene Eocene thermal maximum hydrate destabilization written by D.J. Lunt and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unraveling Deep ocean Connections to Climate with Deep sea Coral Records of Radiocarbon and Cd Ca written by Selene Farrell Eltgroth and published by . This book was released on 2006 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Biotic Response of Deep ocean Ostracodes Across the Paleocene Eocene Boundary written by Elizabeth Abbott Landau and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A high-resolution ostracode faunal study at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau, Southern Indian Ocean. ~1,100 meters paleodepth) through the Paleocene-Eocene Thermal Maximum (PETM) rapid global v arming event (~55 Ma) has revealed abrupt faunal turnovers associated with ocean warming and acidification. The PETM is marked by a transient carbon isotope excursion (CIE) of -2-30 which is broken into three time-intervals for fauna l comparisons: Pre-CIE, CIE. and Post-CIE. Ostracode accumulation rates, abundance, and richness decreased during the ClE but subsequently recovered. Cluster and ordination analyses show distinct differences among fauna before, during, and after the CIE. Site 738 ostracode faunal changes are compared to previous work by Steineck and Thomas (1996) on Site 689 to begin a global synthesis of ostracode faunal response. Similar generic turnover occurs at both sites, with typically infaunal genera appearing in higher percentages during and after the CIE. Platycopids, a clade of epifaunal suspension-feeding ostracodes, are proposed by Whatley and co-workers to be preadapted to low-oxygen conditions. Percent platycopids were therefore predicted to increase during the CIE. a time of presumed decreased dissolved-oxygen concentration in deep- and intermediate-waters. However, at both sites, platycopid percentages do not increase until the post-CIE recovery interval. This platycopid increase is coeval with a well-documented increase in benthic foraminifera taxa associated with high surface export-production environments, leading us to hypothesize that increased food availability may play a more direct role in the observed platycopid increase during the post-CIE.
Download or read book Grain Size Variability Spanning the Paleocene eocene Thermal Maximum in Laramide Basins written by Delaney Todd and published by . This book was released on 2021 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Paleocene-Eocene Thermal Maximum (PETM) is an extensively studied global warming event occurring approximately 56 Ma and lasting around 200 kyr. Marked by a negative 13C excursion from a massive influx of CO2 to the atmosphere, the PETM caused environmental alterations including increases in global temperature, changes in hydrology and ocean chemistry, and floral and faunal overturns. Evidence of these alterations during the PETM is found within both marine and continental basins. During the early Paleogene, the Laramide Orogeny formed a series of nonmarine basins within the Western Interior of the United States. Three of these basins, the Bighorn and Hanna Basins in Wyoming and the Piceance Basin in Colorado, are known to hold continuous depositional records spanning the PETM. In each of these three basins, coincident with the main body of the PETM, there occurs at least one unusually large, amalgamated fluvial sand body that is distinct from sand bodies in the underlying and overlying stratigraphy.
